Chassis actuators of said type are being increasingly used in so-called “active” chassis. There, said chassis actuators serve for example for toe or camber adjustment or for adjusting the vehicle ride height. Said adjustment is made possible in that the actuator has two actuator components which are movable relative to one another, one of which actuator components is arranged on a first chassis part and the other of which is arranged on a second chassis part. The two actuator components are connected by means of a ball screw which in turn can be driven by means of an electric motor which can be actuated by means of a suitable control device. When the electric motor is in operation, the nut is rotated relative to the spindle by means of the electric motor, which spindle is, as a result, displaced axially, thereby effecting the axial adjustment of the actuator components and, as a result, the adjustment of the chassis.
A problem with such chassis actuators is that forces acting externally on the chassis actuator, that is to say forces which are introduced into the actuator via the chassis itself, can lead to an unintentional adjustment of the actuator and therefore of the selected chassis setting, for which reason said forces must be absorbed or the actuator must be fixed in the selected adjustment position. This may be realized directly by means of the electric motor itself, that is to say said electric motor is provided with a continuous supply of electrical current in order to hold the actuator in the desired position. This however involves a large amount of expenditure in terms of control and also with regard to energy balance.
DE 38 36 255 C2 discloses a chassis actuator of the type mentioned in the introduction, in which, aside from a planetary gear set which couples the rotor in terms of movement to the nut and which is of complex design, an electromagnetic jaw clutch is provided for blocking the spindle nut when the electric motor is not supplied with electrical current. Said jaw clutch comprises a clutch disk which is arranged in an axially movable but non-rotatable manner on a collar, which faces away from the electric motor, of a spindle nut flange. The clutch disk is preloaded in the direction of the end wall of the actuator housing by means of a spring. By means of in each case one spur toothing on the clutch disk and the inner side of the end wall, it is possible in the engaged state of the clutch disk to obtain a positively locking connection of the clutch disk to the end wall, and to thereby obtain blocking of the spindle nut and of the threaded spindle. For decoupling of the claw clutch, an annular magnet is provided on the side of the spring, which annular magnet, when excited, pulls the clutch disk out of the spur toothing counter to the force of the spring, and consequently eliminates the blocking action. It is thus possible by means of said blocking device for the actuator to be fixed in position by purely mechanical means when the electric motor is not actuated. However, firstly, the design involves a high level of expenditure from both a structural and also a functional aspect, and secondly, a simultaneous supply of electrical current is always necessary both to the electric motor and to the annular magnet which opens the jaw clutch. If a supply of electrical current to the annular magnet is not possible on account of a fault, an adjustment of the actuator is not possible.